The invention relates to an adhesive label for an article to be labeled, in particular for a film cartridge (for example 35 mm film) for cameras, the adhesive label coding machine-readably properties of the article, in particular of a film in the film cartridge, by the position of at least one boundary between an electrically conductive layer and an electrically nonconductive layer lying thereover. The coding may be a so-called CAS ("Camera Auto Sensing") coding, which contains information on the photographic film contained--film speed, film length and exposure tolerance.
The coding takes place by defined arrangement of electrically conducting and nonconducting fields or their common boundaries at a fixed point on the film cartridge, the electrically conducting fields being interconnected electrically conductively. The items of information are scanned by an electrically active system--comprising two rows of contacts in the camera housing. In this case, current is introduced via one contact each per row, and then, depending on the field scanned (conductive or nonconductive), a current flow can be detected or not detected via the contacts following in the row. The respective combination of current-carrying contacts then provides the corresponding information, which is processed by the camera.
Until now, the cartridge sleeves have been printed on directly. The CAS coding is in this case achieved by the conductivity of the sleeve material, which is covered by electrically insulating printing inks at the points which are not to be conducting, so that no current can flow at these points via the contacts of the CAS system when the cartridge is inserted into the camera.
In the case of a number of private brands, the cartridge sleeves are provided with a combination of direct printing and adhesive label, it not having been possible in any case so far for the CAS coding to be integrated in the label, but instead always having been realized by means of the direct printing.
In these cases, the labeling takes place each time after the assembly of the cartridges, so that the label as such can be perceived and distinct compromises have to be made with regard to design. In the case of this process, there is also the risk of the label and coding having different film types and consequently that mix-ups with serious consequences can occur.
The cartridges comprise the following components: cartridge sleeve, winding spindle, lid, base and sealing lips of felt at the film exit opening.
The cartridge sleeves are formed from a 0.3 mm thick, chromium-plated steel sheet. The printing onto the sheets takes place by offset printing or a combination of offset printing with screen printing, in any case a special, highly scratch-resistant, electrically nonconducting printing ink being printed repeatedly (at least twice) over itself in the region of the CAS coding.
The nonconducting printing ink, which insulates established CAS fields, must withstand unharmed the abrasive stress occurring in practice due to the contacts, since otherwise erroneous items of information are read out due to unintended current flow and the film is incorrectly exposed. The high ink layer thickness of the repeated overprinting of a special, highly scratch-resistant printing ink is consequently indispensable in the region of the CAS coding due to the necessity of achieving a high abrasion resistance.
As the next step, the punchings necessary for forming the film opening are carried out on the printed-on metal sheet and then the metal sheet is cut into strips suitable for the cartridge-assembly machine. The strips are delivered to the film manufacturer in this form. Alternatively, the punching out of the lips for the film opening and the cutting into strips does not take place until at the film manufacturer's.
There, the prefabricated sheet-metal strips are introduced from a stack into the assembly machine and, from the left and right, the sealing lips are fed in from a roll and adhesively bonded (in some cases the sealing lips are also already applied in advance in a separate operation). After cutting off an individual blank from the strip, this is bent into a sleeve and the cartridge is completed by inserting the winding spindle and flanging on base part and lid part.
The charging of the cartridges with the photographic film takes place either in a separate operation after completion of the cartridge or in combination with the insertion of the winding spindle.
Photographic films are offered in a large number of types, color negative films, black-and-white films, slide films, various film speeds, various film lengths, special fabrications for promotional purposes, private brands, etc. A range of over 100 types, up to 250, is therefore normal for a film manufacturer.
Involved with this is the logistical problem of having the correspondingly printed-on sheet-metal strips available for the individual types at the required time and in the required quantity. This means that an adequate quantity of the most popular types (normally about 20) has to be kept constantly in stock and less popular types have to be ordered in good time.
Since the sheet-metal blanks are heavy and voluminous, a large storage capacity is taken up, which causes high costs. If, on the other hand, stock-keeping is reduced to a minimum, flexibility automatically suffers as a result, since types not in stock have first to be procured.
When a label is used, metal sheet and printing are separated from each other, in that the printing and the forming of the boundary is applied completely to an adhesive label. Stock-keeping can be adapted to the capacity of the cartridge assembly, i.e. cut back to a minimum. In an ideal case, the storage of the cartridge material can be reduced to one type, that is the unprinted type, because the types are established only by the labeling. The storage of what is needed for the individual types can take place compactly--and consequently in a space-saving and cost-saving manner--in label rolls.
Since direct printing is no longer needed, there is no longer any necessity to work in the formats which are specified for this and laborious to handle, but instead the metal sheet can be fed directly to cartridge production as a continuous strip.
In further steps, replacement of the sheet-metal cartridges by prefabricated plastic cartridges is also conceivable, since it is no longer essential to use the conductivity of the cartridge material.
The labeling of the film cartridges makes it possible for the abrasion resistance to be achieved not only by the customary process of overprinting highly scratch-resistant special inks but also by an overlamination, or to be made unimportant as a functional criterion by partially applying a conductive layer only in the corresponding regions which are to be conductive.
As a result, labeling is associated with an enormous expansion in the possible forms of design, ranging up to high-quality halftone printing, whereby the label can be given an attractive and promotionally effective design, for example multicolored, high-gloss, with tone shading. The label can additionally be provided with an optically scannable bar code.
It has been attempted to stick over CAS codings already on film cartridges an adhesive label bearing a different coding in order to change the scanned film speed. These adhesive labels contain a single unprotected metal layer, exposed to corrosion, or a single, nonmetallic base layer, which is partially printed with sensitive and unprotected conductive ink. Such labels may be adequate for the occasional changing of the film speed, but are not reliable enough for standard use in the mass production of film cartridges.